It is well known to have control arrangements that automatically place a transmission in neutral if the electrical or hydraulic systems malfunction. Likewise, there are electro-hydraulic power arrangements that automatically condition the transmission to a preestablished speed ratio whenever an electrical malfunction occurs with a transmission being operated in a selected range of ratios. Also known are electro-hydraulic servo systems in which the output from the servo system is either hydraulically or mechanically locked in the event that the electrical input signal to the servo system varies from a predetermined range of values. It is desirable to provide a simple hydraulic interlock that maintains the transmission in the selected speed ratio in the event there is a malfunction in the system's electrical energy.
The present invention is directed to overcoming one or more of the problems as set forth above.